DE102014105439B4 - Flow control valve for a dual fuel fuel injection system - Google Patents

Abstract

Flow control valve for a dual-fuel fuel injection system 5 A flow control valve has a valve body which can be adjusted between a closed and an open position by means of a delivery fluid pressure, and an integrated control valve via which the valve body can be adjusted independently of the delivery fluid.

Description

The invention relates to a quantity limiting valve for a dual-fuel fuel injection system, according to the preamble of claim 1.

In the EP 2 423 498 A1 describes a quantity limiting valve for a large diesel engine, which has an axially adjustable valve body in a valve chamber, which is biased by a spring element against an inlet-side valve seat. When a fuel injection process begins, the pressure on the output side at the quantity limiting valve is reduced, as a result of which the valve body is lifted out of the valve seat and fuel can pass through the quantity limiting valve. As soon as the injection process has ended, pressure is built up again on the output side, as a result of which the valve body is moved back into the closed position.

DE 10 2005 036 780 A1 describes a fuel injection system which, with a mechanically simple structure and low control effort, achieves a high level of operational reliability by providing a quantity limiting arrangement with a quantity limiting valve and a bypass valve upstream of a respective injection injector.

DE 10 2008 014 250 A1 describes a common rail fuel supply system of an internal combustion engine, with a low pressure area, with a pump device comprising at least one high pressure pump, in order to deliver fuel from the low pressure area of the fuel supply system into a high pressure area thereof.

DE 11 2012 004 430 T5 describes a dual fuel system having a dual fuel injector having a gaseous fuel inlet, a gas nozzle outlet set, a liquid fuel inlet, and a liquid nozzle outlet set. Disposed in the dual fuel injector is a gas nozzle chamber that is fluidly connected to the gaseous fuel inlet and a liquid nozzle chamber that is fluidly connected to the liquid fuel inlet.

The invention is based on the object of creating a compact volume control valve with variable adjustment options using simple structural measures.

This object is achieved with the features of claim 1. The subclaims indicate appropriate further training.

The quantity limiting valve according to the invention is used to control the flow of a conveying fluid which is passed through the quantity limiting valve. The delivery fluid is, for example, a gaseous medium, with liquid media also being considered in principle. The quantity limiting valve is used for a dual-fuel fuel injection system of an internal combustion engine, in which the internal combustion engine can be operated both with fuel gas, in particular in the pilot jet process, and with liquid fuel, in particular with diesel fuel, biofuel or heavy oil. In such a dual-fuel fuel injection system, this is
Quantity limit valve preferably assigned to a fuel gas injector unit. However, it is also possible to additionally or alternatively assign the quantity limiting valve to a liquid fuel injector unit.

The quantity limiting valve has a valve body which can be adjusted between a closed and an open position, a flow channel being released for the delivery fluid in the open position and the flow channel being blocked in the closed position. The actuating movement of the valve body is controlled by the pressure of the delivery fluid.

A control valve is also integrated in the housing of the quantity-limiting valve in order to be able to adjust the valve body between the open and closed positions regardless of the pressure of the delivery fluid. This makes it possible to close the flow control valve even in such situations and thus to interrupt the flow of the delivery fluid in which the delivery fluid pressure assumes a value at which the valve body is in the open position. The control valve acts on the valve body in the open position and adjusts it to the closed position. The control valve thus allows the quantity limiting valve to be closed in additional situations regardless of the pressure of the delivery fluid. It is in particular possible to close the quantity limiting valve via the control valve if the valve body is in the open position due to the current pressure of the delivery fluid.

The control valve is integrated in the housing of the flow control valve, so that no additional space is required for the control valve and there is an overall compact flow control valve. The quantity limiting valve can optionally be integrated in the injector unit.

According to an advantageous embodiment, the control valve is designed passively without its own energy supply, so that there is no electrical, pneumatic or hydraulic actuator in the control valve for the Carrying out the actuating movement is necessary. According to an alternative embodiment, however, it can also be expedient to actively design the control valve and to provide it with such an electrical, pneumatic or hydraulic actuator, for example an electromagnetic actuator, the actuation of which moves the valve body. The actuator of the actively designed control valve is preferably to be switched via control signals that come from a sensor system in the fuel injection system, for example a pressure sensor.

According to an expedient embodiment, an actuating element of the control valve, which forms the valve member of the control valve and acts on the valve body of the quantity-limiting valve, is adjusted via a control fluid. In particular when the quantity limiting valve is used in a fuel injection system, the liquid fuel which is under pressure in the fuel injection system and is supplied to an injector unit can be used as the control fluid. It is possible, for example, to branch off part of the liquid fuel under pressure via a control line and to feed it to the control valve for actuating the actuating element. This design has the advantage that the control element is designed to be passive and active control of the control element with its own energy supply is not necessary. Rather, the control takes place via the liquid fuel, pressure changes in the supplied liquid fuel leading to an actuating movement of the control element of the control valve.

According to the invention, the quantity limiting valve is used in a dual-fuel fuel injection system which comprises a fuel gas injector unit and a liquid fuel injector unit. The quantity limiting valve is preferably assigned to the fuel gas injector unit, but in principle it can also be assigned to the liquid fuel injector unit. The flow control valve is located in the flow path to the injector unit and is able to interrupt the flow of fluid to the injector unit. The flow control valve is blocked depending on the delivery fluid pressure by moving the valve body of the flow control valve from the open to the closed position when the mean pressure drops below a pressure threshold during an injection process. On the other hand, even in the event of a malfunction in the injection system, for example if the valve body is not automatically adjusted to the closed position, the valve body can be moved to the closed position by actuating the integrated control valve. This is done by changing the pressure of the control fluid, which is the liquid fuel in the dual-fuel fuel injection system. With a correspondingly high change in pressure of the control fluid, the control element of the control valve is adjusted from the non-functional to the functional position, in which the control element moves the valve body into the closed position.

According to the invention, the quantity limiting valve for a dual-fuel fuel injection system has a valve body which can be adjusted between a closing and an opening position, a flow channel being released for a conveying fluid in the quantity limiting valve in the opening position and the flow channel being blocked in the closing position. The actuating movement of the valve body depends on the fluid pressure. A control valve is integrated in a housing of the flow control valve. Via the control valve, the valve body can be adjusted between the open and closed positions independently of the delivery fluid. The dual-fuel fuel injection system has a control line which is connected to a liquid fuel injector unit, an adjustable pilot valve being arranged in the control line and control fluid being able to be supplied to the quantity-limiting valve downstream of the pilot valve.

The valve body of the quantity-limiting valve is advantageously acted upon by a spring element in its open position. According to a further advantageous embodiment, the control element of the control valve is acted upon by a spring element into its non-functional position, in which the valve body is not influenced by the control element. By actuating the actuating element, for example via the control fluid, the actuating element is adjusted against the force of the spring element acting on it from the non-functional position into the functional position and can move the valve body against the force of the spring element acting on it from the open position into the closed position.

The control element of the control valve is moved back into the non-functional position by the force of the spring element as soon as the pressure conditions in the control fluid adjust accordingly. This is the case with a dual fuel fuel injection system when it is working properly.

According to a further expedient embodiment, a throttle is integrated in the control line of the control fluid, at which there is a pressure drop in the control fluid which can be used to control the control valve. For example, the higher pressure upstream of the throttle is fed to the actuating element, so that the increased pressure puts the actuating element in the non-functional position and holds it in this position. If the pressure in the control line drops, the actuating element moves into its functional position due to the spring force effect and moves the valve body into the closed position.

The control element of the control valve is adjusted when a minimum pressure is exceeded. The adjustable pilot valve is arranged in a control line, which is connected to the liquid fuel injector unit in a dual-fuel fuel injection system, the control line opening downstream of the pilot valve into a fuel reservoir and the pressure of the control fluid being tapped for the actuating movement of the control valve. The throttle is expediently located downstream of the pilot valve, the pressure being tapped directly upstream of the throttle for the control of the control valve. The pilot valve, for example a 2/2-way valve, switches in time with the injection in the liquid fuel injector unit, the pressure downstream of the pilot valve being reduced when the pilot valve is closed and being built up when the pilot valve is open. Here, a medium pressure is set which is above the minimum pressure which is required to keep the control valve in the non-functional position. By contrast, the minimum pressure is no longer reached if the pilot valve remains closed in the event of a malfunction, whereupon the control valve is moved into the functional position for closing the valve body.

According to a further expedient embodiment, the control element of the control valve is designed as an actuating piston which is adjustable in a piston receiving space in the quantity-limiting valve. At least one side of the actuating piston or of a component connected to the actuating piston is acted upon by the control fluid in order to hold the actuating piston in the non-functional position against the force of the spring element. According to a further expedient embodiment, both opposite end faces of the actuating piston or of the component connected to the actuating piston are acted upon by the control fluid, but at different pressures, in particular the pressure upstream and downstream of the throttle in the control line. This embodiment has the advantage that the volume displacement in the piston receiving space that occurs during an actuating piston movement can be dissipated via the connection to the control line. In addition, any fault currents are diverted directly between the two chambers of the piston receiving space on opposite sides of the actuating piston or of the component connected to the actuating piston without impairing their function.

• 1 in schematischer Darstellung ein Dual-Fuel-Kraftstoffeinspritzsystem für eine Brennkraftmaschine, mit einer Flüssigkraftstoff-Injektoreinheit und einer Brenngas-Injektoreinheit, der ein Mengenbegrenzungsventil zugeordnet ist,
• 2 das der Brenngas-Injektoreinheit zugeordnete Mengenbegrenzungsventil im Längsschnitt.

Further advantages and expedient designs can be found in the further claims, the description of the figures and the drawings. Show it:

• 1 a schematic representation of a dual-fuel fuel injection system for an internal combustion engine, with a liquid fuel injector unit and a fuel gas injector unit, to which a quantity limiting valve is assigned,
• 2nd the flow control valve assigned to the fuel gas injector unit in longitudinal section.

In the figures, the same components are provided with the same reference symbols.

This in 1 Dual fuel fuel injection system shown 1 is set up for operation with both liquid fuel, for example diesel fuel or heavy oil or bio oil, as well as for operation with fuel gas, for example natural gas or biogas in the ignition jet process. The dual fuel fuel injection system 1 includes a dual fuel injector system 2nd as well as a high pressure gas storage 3rd A fuel gas flow control valve to hold the fuel gas under pressure 4th which from the high pressure gas storage 3rd is fed, and in the fuel section two series-connected pumps 5 and 6 as well as a liquid fuel reservoir 7 . The dual-fuel injector system 2nd comprises a liquid fuel injector unit 8th and a fuel gas injector unit 9 , via which liquid fuel or fuel gas can be injected into the combustion chamber of an internal combustion engine.

It also belongs to the dual-fuel injector system 2nd a high pressure accumulator 10th for the liquid fuel of the two pumps connected in series 5 and 6 - a low pressure pump and a high pressure pump - is supplied with high pressure liquid fuel. The high pressure accumulator 10th is either arranged in the injector unit or designed as a common-rail high-pressure accumulator outside the injector unit. The high pressure accumulator 10th is a liquid fuel flow control valve 11 downstream, that in a high pressure line 12th is arranged, which to the liquid fuel injector unit 8th leads. From this high pressure line 12th branch inflow control lines 13 and 14 each with a throttle to control the liquid fuel injector unit 8th or the fuel gas injector unit 9 . The one through the inflow control lines 13 , 14 led fuel provides the control fluid to control the injector units 8th , 9 represents.

That of the liquid fuel injector unit 8th Control fluid supplied flows through a backflow control line 15 in which there is a pilot valve 16 located to the liquid fuel reservoir 7 . The pilot valve 16 is designed as a 2/2-way valve, for example. In the control line section between the pilot valve 16 and the fuel reservoir 7 there is a throttle 17th , also in the inflow Control lines 13 and 14 to the injector units 8th , 9 and in the backflow control line 15 upstream of the pilot valve 16 .

On the gas side flows from the high pressure gas storage 3rd the fuel gas to the fuel gas flow control valve 4th and on over a line 18th to the fuel gas injector unit 9 . The control of the injector unit 9 takes place via the liquid fuel, which via the inflow control line 14 is fed. On the outflow side, the control fluid comes from the inflow control line 14 via a return flow control line 19th dissipated into a throttle and downstream a control or pilot valve 20th is integrated. Downstream of the valve 20th opens the return flow control line 19th in the return flow control line 15 the liquid fuel injector unit 8th upstream of the throttle 17th .

The dual-fuel fuel injection system operates during the starting process of the internal combustion engine 1 preferably exclusively with fuel injection via the liquid fuel injector unit 8th . At higher speeds, you can switch to gas operation using the ignition jet method, using the liquid fuel injector unit 8th a pilot injection takes place.

In 2nd is the fuel gas flow control valve 4th shown in longitudinal section. The flow control valve 4th has a housing 21 and a flange piece facing the front of the injector inlet 22 that about a cap nut 23 with the housing 21 connected is.

In the housing 21 is a gas room 24th formed in the via a connector 25th on the the flange piece 22 axially opposite side, gas flows in from the high-pressure gas storage as indicated by the arrow. In the gas room 24th can be a piston-shaped valve body 26 move axially, in the wall of an axially extending overflow channel 27 is introduced, via which the gas from the gas space 24th to an outflow channel 28 in the flange piece 22 arrives, from which the gas as indicated by the arrow from the fuel gas flow control valve 4th derived and continued in the direction of the injector unit.

The valve body 26 is by a spring element 29 applied to its open position. The valve body 26 is in a recording room 30th recorded and can be in the recording room 30th can be adjusted axially. By the force of the spring element 29 becomes the valve body 26 held in its open position in which the valve body 26 axially partially into the gas space 24th protrudes and gas from the gas space 24th over the overflow channel 27 to the outflow channel 28 reached. Will the valve body 26 completely or largely completely in the recording room 30th inserted, the overflow channel is located 27 outside the flow connection with the gas space 24th , so that the flow connection is interrupted; the valve body is thus in a closed position in which the flow flows through the flow control valve 4th is interrupted.

The one in the gas room 24th prevailing pressure of the fuel gas introduced acts on the facing end of the valve body 26 and presses it against the force of the spring element 29 in the closed position. At the same time there is in the recording room 30th , in which the valve body 26 can also move a gas pressure that the valve body 26 applied to the open position. If the gas pressure on both ends of the valve body 26 is at least approximately the same height, the valve body 26 by the force of the spring element acting on it 29 held in the open position. However, the gas pressure on the gas space drops 24th away from the side, so the valve body 26 by the pressure in the gas space 24th adjusted to the closed position.

In the case 21 of the flow control valve 4th is a control valve 31 integrated, its control element 32 is designed as an actuating piston which is coaxially and axially offset from the valve body 26 is arranged. The actuating piston is in a closed piston receiving space 33 axially adjustable and received by a spring element 34 in the direction of a functional position in which the actuating piston 32 the valve body 26 axially moved to the closed position. The actuating piston 32 is with a head 35 connected to the piston receiving space 33 divided into two chambers, the spring element 34 on the the piston 32 opposite side of the head 35 attacks.

The piston receiving space 33 is on this side and beyond the head 35 via control channels 36 and 37 with control lines 38 and 39 ( 1 ) connected immediately upstream and downstream of the throttle 17th in the backflow control line 15 branch which to the liquid fuel reservoir 7 leads. The control channels 36 and 37 are in the flange plate 22 or the housing 21 brought in. Between the flange plate 22 and the housing 21 there are sealing rings 40 , 41 and 42 that the control channels 36 and 37 seal radially.

Via the first control channel 36 with the control line 38 is connected, liquid fuel as a control fluid under relatively high pressure in the chamber of the piston receiving space 33 with the control piston 32 guided. The opposite chamber of the piston receiving space 33 in which the spring element 34 is arranged is via the second control channel 37 with the control line 39 downstream of the throttle 17th connected at which there is a lower pressure. This pressure difference acts on the control element with the control piston and the head against the force of the spring element 34 in the withdrawn non-functional position. If the pressure difference falls below a threshold value, the resulting force of the hydraulic differential pressure drops on the head 35 under the spring force of the spring element 34 and the actuating piston 32 is axially adjusted from the non-functional to the functional position, in which the front end of the actuating piston against the valve body 26 presses and the valve body 26 in its closed position.

The pilot valve opens and closes during fuel injection operation 16 in the timing of the injection. This creates a medium pressure in the return flow control line 15 downstream of the pilot valve 16 that over the control line 38 and the control channel 36 into the chamber of the piston receiving space 33 with the control piston 32 to be led. In normal operation, the medium pressure exceeds the threshold value relevant for maintaining the non-functional position, so that the control element of the control valve 31 is held in the non-functional position.

On the other hand, if the medium pressure drops immediately upstream of the throttle due to a fault, for example 17th below the threshold, for example when the pilot valve is permanently closed 16 the case is, the pressure in the chamber of the piston receiving space drops accordingly 33 with the adjusting piston so that the spring element 34 pushes the control piston into the functional position and this pushes the valve body 26 closes.

If the pilot valve 20th that of the fuel gas injector unit 9 assigned, remains open due to malfunction and at the same time that of the liquid fuel injector unit 8th associated pilot valve 16 is closed due to malfunction, the valve body 26 of the flow control valve 4th also moved to the closed position while the control valve 31 remains in its inoperative position.

If that's the fuel gas injector unit 9 associated pilot valve 20th remains open, the liquid fuel quantity limiting valve advantageously closes 11 , so that the flow control valve 4th closes.

Claims (14)

Quantity limiting valve for a dual-fuel fuel injection system (1), with a valve body (26) adjustable between a closing and an opening position, a flow channel (27) being released for a conveying fluid in the quantity limiting valve (4) in the opening position and the flow channel () in the closing position 27) is blocked, the actuating movement of the valve body (26) depending on the delivery fluid pressure, characterized in that a control valve (31) is integrated in a housing (21) of the quantity limiting valve (4), via which the valve body (26) is independent of the delivery fluid is adjustable between the open and closed positions, the dual fuel fuel injection system having a control line (15) which is connected to a liquid fuel injector unit (8), an adjustable pilot valve (16) being arranged in the control line (15) and Control fluid can be fed downstream of the pilot valve (16) to the quantity limiting valve (4). Flow limiting valve after Claim 1 , characterized in that an actuating element (32) of the control valve (31) acting on the valve body (26) is adjustable via a control fluid. Flow limiting valve after Claim 1 or 2nd , characterized in that the actuating element (32) of the control valve (31) is designed as an actuating piston, wherein a piston receiving space (33) in which the actuating piston is received is acted upon by the control fluid. Flow limiting valve after Claim 3 , characterized in that the opposite end faces of the actuating element (32) or a component connected to the actuating element (32) are acted upon by the control fluid with different high pressures. Flow control valve according to one of the Claims 1 to 4th , characterized in that a throttle (17) is integrated in the control line (15) of the control fluid. Flow limiting valve after Claim 4 or 5 , characterized in that the opposite end faces of the control element (32) or of the component connected to the control element (32) are acted upon by the control fluid upstream and downstream of the throttle (17). Flow limiting valve according to one of the Claims 1 to 6 , characterized in that the valve body (26) and the actuating element (32) of the control valve (31) are arranged coaxially. Flow control valve according to one of the Claims 1 to 7 , characterized in that the valve body (26) is acted upon by a spring element (29) in its open position. Flow control valve according to one of the Claims 1 to 8th , characterized in that the actuating element (32) of the control valve (31) is acted upon by a spring element (34) in its non-functional position. Flow control valve according to one of the Claims 1 to 9 , characterized in that the conveying fluid is a fuel gas. Flow control valve according to one of the Claims 1 to 10th , characterized in that the control fluid is a liquid fuel. Dual fuel fuel injection system with a flow control valve according to one of the Claims 1 to 11 , with a fuel gas injector unit (9) and the liquid fuel injector unit (8). Dual fuel fuel injection system after Claim 12 , characterized in that the quantity limiting valve (4) is assigned to the fuel gas injector unit (9). Method for operating a dual fuel fuel injection system according to Claim 13 , in which the liquid fuel is used as a control fluid and the control valve (31) is adjusted via the pressure of the control fluid.

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